The present invention relates to a short-circuit member assembly for short-circuiting predetermined segments, a commutator including the short-circuit member assembly, and a motor including the commutator.
A motor including a commutator, such as a direct current (DC) motor, includes power feeding brushes and an armature. The power feeding brushes slide along and contact the commutator. The armature includes armature coils and an armature core. The armature coils are electrically coupled to the commutator. The armature core has a plurality of teeth, around which the armature coils are wound. A plurality of segments are arranged on the outer circumference of the commutator. The number of the segments is normally the least common denominator of the number of magnetic poles of magnets used in a stator (the number of field poles) and the number of the teeth (the number of salient poles). In such a commutator, predetermined segments must be short-circuited so that they have the same potential. For example, Japanese Laid-Open Patent Publication No. 2005-137193 describes a commutator that integrally includes a plate-like short-circuit member assembly for short-circuiting predetermined segments.
The short-circuit member assembly described in the publication includes first and second shirt-circuit member groups, which are superimposed with each other. Each short-circuit member group includes plate-like short-circuit pieces, the quantity of which is the same as the segments of the commutator. The short-circuit pieces are arranged in the circumferential direction of the commutator. Each short-circuit piece includes an outer terminal, which is arranged outward in the radial direction, an inner terminal, which is arranged inward from the outer terminal in the radial direction, and a connecting portion, which connects the outer terminal and the inner terminal. Each outer terminal includes an engagement portion, which extends outward in the radial direction. The outer terminals of the first short-circuit member group and the outer terminals of the second short-circuit member group are superimposed with each other, and the inner terminals of the first short-circuit member group and the inner terminals of the second short-circuit member group are superimposed with each other. The outer terminals that are superimposed with each other are joined with one another, and the inner terminals that are superimposed with each other are joined with one another. This integrates the short-circuit member groups. The engagement portions each have a basal end connected to the corresponding segment. The engagement portions each project outward in the radial direction from the corresponding segment. The armature coils each have a distal end engaged with a predetermined one of the engagement portions.
The short-circuit member assembly described above is manufactured by superimposing and joining all the outer terminals included in the first short-circuit member group and all the outer terminals included in the second short-circuit member group, and superimposing and joining all the inner terminals included in the first short-circuit member group and all the inner terminals included in the second short-circuit member group on top of each other. In this case, many portions of the two short-circuit member groups must be joined with one another. This complicates the manufacture of the short-circuit member assembly.